Generator.prototype.throw()
The throw()
method resumes the execution of a generator by throwing an error into it and returns an object with two properties done
and value
.
Syntax
JavaScript
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<var>gen</var>.throw(exception)
Parameters
exception
- The exception to throw. For debugging purposes, it is useful to make it an
instanceof
Error
.
Return value
An Object
with two properties:
done
(boolean)- Has the value
true
if the iterator is past the end of the iterated sequence. In this casevalue
optionally specifies the return value of the iterator. - Has the value
false
if the iterator was able to produce the next value in the sequence. This is equivalent of not specifying thedone
property altogether.
- Has the value
value
- any JavaScript value returned by the iterator. Can be omitted whendone
istrue
.
Examples
Using throw()
The following example shows a simple generator and an error that is thrown using the throw
method. An error can be caught by a try...catch
block as usual.
JavaScript
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function* gen() { while(true) { try { yield 42; } catch(e) { console.log("Error caught!"); } } } var g = gen(); g.next(); // { value: 42, done: false } g.throw(new Error("Something went wrong")); // "Error caught!" // { value: 42, done: false }
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Generator.prototype.throw' in that specification. |
Standard | Initial definition. |
ECMAScript 2017 Draft (ECMA-262) The definition of 'Generator.prototype.throw' in that specification. |
Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | ? | 26 (26) | ? | ? | ? |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | ? | ? | 26.0 (26) | ? | ? | ? |
See also
License
© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-us/docs/web/javascript/reference/global_objects/generator/throw